600+ Range For Cybertruck

[firsttruck]

Interesting thought though... Even if the Semi has 4x the cells of the CT, the Semi is supposed to be fully laden fir the 621 range. So even if the CT is “only” towing a 14,000 lb trailer there should be plenty of range available.

Not only is the Semi wider & longer than Cybertruck, but the Semi is much taller with the driver area much higher above the roadway.

There could be two or three layers of battery in the Semi.

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[T3slaDad]

I wonder how much energy the semi can recapture with regen braking. Towing a heavy load, I could see regen going crazy when controlling downhill speeds!

If love to hear about regen data, anyone know of some off hand for Teslas in general?

And after a little digging, this article lays out some research: https://electrek.co/2018/04/24/regenerative-braking-how-it-works/

 

[Crissa]

If love to hear about regen data, anyone know of some off hand for Teslas in general?

From a driver's point of view, it feels like engine braking. Because, mechanically, that's what it is.

There's a cap of how much energy can be recovered, at that point the motor just spins faster as the battery management system takes smaller slices of power. But the slices are so tiny that you can't feel them, it just feels like smooth, heavy deceleration.

The amount of energy you capture is then a narrow band between how fast you're going, on how much slope, with how much weight.

And as pointed out, with a trailer, unless the trailer also has regenerative braking, those axles will have to apply some amount of friction braking to maintain control.

-Crissa

 

[ajdelange]

I wonder how much energy the semi can recapture with regen braking.

Maybe quite a lot, maybe none. If the rest of this and the following two paragraphs get to be too much skip ahead to the fourth. Depends on how the driver manages it. Let's say the truck is at the top of a hill. It has lots of potential energy in it (m*g*h). The brake is released and the truck starts to roll down the hill picking up speed as it goes. It will accelerate up to the speed at which the drag and rolling resistance are equal to the gravitational component parallel to the road surface. The truck will then stay at constant speed. For each meter it descends it will lose m*g*1 unit of potential energy and that will be converted to heat warming the air the truck pushes out of the way, the bearlngs and side walls. Eventually the truck comes to the bottom of the hill and the gravitational pull along the road bed goes to 0. Now the drag and rolling resistance forces are the only forces and they decelerate the truck which eventually comes to a stop some distance from the bottom of the hill. In this scenario no potential energy has been recaptured. The truck could have been an ICE truck.

Now let's rerun but this time recognize that in the acceleration phase the speed limit will have been exceeded at which point the driver will put his foot on the brake which applies a force against gravity to the point that drag plus rolling resistance just equals gravity and the truck rolls down the hill at constant speed. As before, for each decrease in altitude of 1 m the truck loses m*g*1 unit of potential energy but now all of that does not go to drag and rolling resistance. Some goes to heat dissipated in the brakes. This time the truck arrives at the bottom of the hill but going at a slower speed. Drag and rolling (let's call them D&R) once more slow the truck to a stop but it will come to rest closer to the bottom of the hill than in the case where no brakes were applied. In the first instance all the potential energy of the truck was used to do the useful work of overcoming D&R. In the latter case some of that was wasted on brake heating so the truck did not go as far.

In a third run we now suppose a BEV. As the speed picks up to the point where the speed limit is about to be exceeded instead of moving his foot to the brake the driver feathers the accelerator pedal and the motors go into generation absorbing torque and thus applying thrust against gravity. Truck rolls downhill at constant speed and reaches the bottom at the speed limit. If the driver now feathers the pedal such that the power meter reads 0 the motors will neither be absorbing nor generating thrust and the truck will coast the same distance as in the ICE truck case. The difference here though is that no potential energy was wasted to brake heat. It was turned into electricity and most (90% or more) of that went back to the battery.

When all is said and done how much regen energy gets captured depends on the terrain and the actual speed profile. If the road is completely level it depends only on the speed profile. Here the energy put into and taken out of the vehicle is kinetic energy (m*v*v/2).

If love to hear about regen data, anyone know of some off hand for Teslas in general?

The Telsa vehicles record the energy consumption of the car. They report the power to you via the power meter and the energy via the Wh/mi display. If power is negative (meaning that energy is being put into the battery instead of being taken out of it) the power meter deflects downwards and it is obvious that regen is occuring and to what extent. Similarly the consumption graphs, if below 0, indicate net energy to the battery (which has to come from regen as it can't come from anywhere else). The graphs display data calculated from the "integral with respect to time" (if you are familiar with that term fine, if not it is simply the cumulative sum of the power measurements). Apparently the integral of the negative power (regen) measurements is available and can be accessed through the CAN bus if you know how to do that but it is not available to the driver. Thus it is not generally apparent how much regen you got on a particular trip. I've had cases where the SoC at the end of a trip is a couple of percent higher than at the outset but that is rare. Clearly I did OK on regen in those cases.

How effective is it? That depends on how you drive as noted above. To get some idea you could turn it off, run around for a couple of weeks, note the Wh/mi over that time (use one of the odometers), turn it back on and compare. I'll mention that one of the things that got a few extra miles of range for the same size battery in the extended mileage X was having the car take over the transition from regen to friction brake at a stop.

 

[KendrickMB]

And as pointed out, with a trailer, unless the trailer also has regenerative braking, those axles will have to apply some amount of friction braking to maintain control.

This made me think of something. I don't tow, so I could have this wrong. With ICE vehicles, the trailer brakes are applied as the vehicle's brakes are applied. When towing with an EV, I assume the same is true when using the brakes. However, when using regenerative braking, does the EV apply the trailer brakes? Or do you have to use the brakes on an EV in order to safely tow a trailer?

I imagine it would be a shame to not be able to use one pedal driving when towing.

 

[ajdelange]

In No. 34 I posted as if the tractor would be able to take advantage of regen from the trailer i.e. the trailer braking would be done by the tractor or, at least, the energy derived from braking the whole rig would revert to the battery. This is, for sure, not the case if one, for example, puts his boat trailer behind his X. When the X brakes the surge brakes on the trailer come on to slow it down or a signal from the brake controller goes to the electric brakes and they absorb the the energy removed. In such cases, of course, there is no regen from the trailer and this is one of the main reasons that trailer towing will have such a major effect on the available range.

The picture is a little different with the Semi. It will be much less flexible than the situation in which the CT owner can buy any of thousands of different trailers from hundreds of different manufacturers. Because regen can save appreciable amounts of energy I can conceive of Tesla either building their own trailer or working with a trailer manufacturer or two to make regenerative braking available for the trailer. This, of course, has many interfacing implications and would require, as a minimum "motors" on the trailer. Huge trade space so I am not suggesting that Tesla would do this. Just suggesting that they might think about it. I have wondered how Tesla might handle braking in the early release Semis.

Or do you have to use the brakes on an EV in order to safely tow a trailer?

I would say that's a contradiction in terms

I imagine it would be a shame to not be able to use one pedal driving when towing.

I really don't see Tesla undertaking the engineering necessary to do what I suggested above in the CT market space so I think we need to accept that it's going to be like an ICE truck with regard to towing. We will not get the benefits of regen from the trailer part of the load. We will continue to get it from the tractor, of course, but at capacity it will represent only about 1/3 of the system load.

 

[KendrickMB]

I really don't see Tesla undertaking the engineering necessary to do what I suggested above in the CT market space so I think we need to accept that it's going to be like an ICE truck with regard to towing. We will not get the benefits of regen from the trailer part of the load. We will continue to get it from the tractor, of course, but at capacity it will represent only about 1/3 of the system load.

Either I'm not understanding something, or maybe I asked my question wrong. I wasn't asking about regen from the trailer, just how the trailer brakes are told to activate by the EV. Let's assume I'm pulling a trailer with a Model X to use a current vehicle as an example. If I'm one pedal driving the X, will the trailer brakes engage when the X's regen braking engages? Or does the brake pedal have to be pressed in order for the trailer brakes to engage?

 

[Crissa]

BTW, it's generally better to not use any sort of braking if it's not needed. Even regen incurs an energy loss when applied. So it's most optimal not to use it except when you intend to slow down quickly. (Or, as said, the hill is giving you more speed than you need, it at least get you some of it back without overheating.)

(Hence one-foot driving such as Tesla's default is actually less efficient. It is safer, but it's less efficient.)

Since regen braking is tied to the accelerator, the physical brakes are not applied. Nor the trailer brakes, AFAIK. You need to actually step on the brakes to do that.

-Crissa

 

[ajdelange]

Either I'm not understanding something,

You're not but the whole idea of sites like this is change that.

Let's assume I'm pulling a trailer with a Model X to use a current vehicle as an example. If I'm one pedal driving the X, will the trailer brakes engage when the X's regen braking engages? Or does the brake pedal have to be pressed in order for the trailer brakes to engage?

I'm not sure I can answer that correctly because i don't know the details of what the Tesla does in tow mode. The Tesla is equipped with a connector for a brake controller. This connector would have a pin that senses and sends the braking signal to the controller. The Telsa illuminates the brake lights whenever the vehicle decelerates at some threshold level. I assume, but I am assuming, that it is this signal which is passed to the controller connector and on to the trailer lights. Thus the controller knows when the vehicle is decelerating and can send a signal proportional to the deceleration (as sensed by its internal sensor) to the brakes in the trailer. Thus I believe the answer to your question is that you can control a conventional trailer with a conventional controller plugged into a Model X harness while engaged in "one pedal" driving.

 

[hobbit11]

He said 600 miles fully laden.

-Crissa

yup

 

[KendrickMB]

Thank you ajdelange and Crissa. I appreciate the explanations a lot.

 

[Riptide]

Those are pretty rarified. And they still have to sit still a number of hours a day.

It's bot how many miles of ragne it has - because charging infrastructure will grow with it - it's how many miles you can go in so many hours, anyhow.

-Crissa

Team driving isn’t rare. It’s very normal for long haul.

 

[fritter63]

He said 600 miles fully laden.

-Crissa

"What is the range of a fully laden Cybertruck?"

"It's not a matter of weight, it's a matter of how it would grip the coconut"....

 

[Crissa]

Team driving isn’t rare. It’s very normal for long haul.

You described team driving going further/longer than they're allowed to in a day, as well as not stopping for anything, which is ridiculous.

-Crissa

 

[Martin Harford]

With FSD maybe the driver is sleeps for 5-6 hours. Car wakes driver up when needed.

Just think of all the DUIs that will be avoided, especially with ticket avoidance mode in full operation!